Powertrain, generic (extended)

P2518 A/C Refrigerant Pressure Sensor B Circuit High

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modeNo

P2518 is stored when pressure sensor B reports a signal close to its supply voltage. GM, which uses B for the low-side sensor in its hybrid tables, sets the limit at 98 % of the reference, about 4.90 V. Interesting is how the rating changed: the 2011 edition counted 40 of 50 samples and treated it as type B with two trips, while the 2016 and 2019 editions make it type A, lighting the lamp after a single failed drive; 2019 needs 4 s out of a 5 s window. Typical causes are a signal conductor shorted to 5 V or battery voltage, an open sensor ground, or water in the connector. A real pressure peak normally stays inside the range and does not trigger it. Compare P2517 for the low extreme and P2516 for a frozen but valid value.

Likely causes

Signal wire shorted to 5 V or battery voltage
Sensor ground open
Moisture or corrosion in the sensor connector

Symptoms

  • Check engine light after one drive on newer GM hybrids
  • A/C compressor disabled, no cooling

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€50–350
Time0.5–2 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

ac pressure sensor bsensor wiring

Related codes

P2515P2516P2517P0533

References: gsi.ext.gm.com, gsi.ext.gm.com, gsi.ext.gm.com.